Abrasive disk



July 7, 1942- N; l-loLms-rL-:N- 2,2881'625 AnRAsIvE nr'sx Filed oct. 18, 1941 f Patented July 7, `1942 f y2,288,625 'y UNITED STATES PATENT oFFlCE ....llsx

Niilo Holmsten, NewpRochelle, Nt Y. l Application October 18, 1941, Serial No. 415,507

16 Claims.

tion will become clear from the following description, appended claims, .and accompanying drawing forming a part of this specification and wherein:

Figure' l isla top plan view of one form of the composite abrasive element constituting the instant invention;

Figure 2 is a section taken on the line 2-2 of IFigure 1; v

Figure 3 is an 'enlarged elevation, partly broken away, of one embodiment of a. backing of the composite abrasive element; and' l Figure 4 is an enlarged elevation, partly broken away, of another embodiment of a backing-o the composite abrasive element.

In view of the details of construction hereafter yset forth, there is provided a composite abrasive element which is characterized by a high tensile strength and a high resistance to shearing. 'I'he composite abrasive element is also sufficiently -stiif so that it will normallylie fiat. with the `result that a smooth. vibrationless Vsanding operation over its entire area is obtained. Inaddition, the composite abrasive element is sumciently resilient and flexible so that it will permit appreciable distortion at any point without breaking. Further,l the composite abrasive element is so constructed that there will be no sepaditions whereby-the free moisture is reducedv to a minimum or even eliminated from the product. After the material has been dried, it is cut into.v disks ofv the desiredv shape and size. If desired, at this stage of the process the exposed surface of the ply-wood backing may be marked by printing or stamping any desired indicia, such as, for example, to identifythe grit numbers and give any other desirable infomation. The disks are then coated on all sides thereof, as by dipping ina solution of a syntheticv resin which sets -upon heating to form a waterproof, heat-resist- (ci. 51--195i I L an elevated temperature until the'resin is' conv-verted into the insoluble, infusible state.

The dipping of the en tlre'disk into the solution of synthetic resin seals the (cut) edges and extends over the face and backing of the disk. The method of application and the subsequent conversion of the resin provides a thin film al1 over the disk whereby the latter is rendered lmpervious to water. Because of this, the product may be used in climates of high humidity without detracting from the value and cutting elliciency thereof. The product can be used outdoors for sanding purposes, such as automobile fenders and the like, even in rainy weather.

adhesion of the grain to the sheet'material (fabric), with the result that premature flying off of the grit during operation is inhibited.

The ply-wood constituting the backing may be zo formed of one or more wood plies. Satisfactory results have been obtained when the backing consists of two or three-ply ply-wood. 'I'hough the ply-wood backing, when'it consists of a plurality of plies, may be constructed with the grains of the plies parallel to each other, I have found that surprising and unexpected results are obtained when the ply-wood backing is constructed so that the grain of each of the plies is angularly disposed with respect to the other. The preferred angular disposition of the grain of the plies with respect to each other depends on the number of plies constituting the backing. a

Inthat embodiment of the invention which utilizes a ply-wood backing consisting of two plies, though the plies may be disposed with respect to eachother so that the grain of one ply is at any angle with respect to the other, best results .are secured when the grain of one ofthe lplies is disposed at approximately right angles 40 to the grain of the other ply.

a In that embodiment of the invention which disposed that the grain of each ply is at any angle withl respect to the others, best results are ob- 45 tained when the three plies are so arranged that in the final ply-wood the grains-of adjacent plies are disposed at an angle of approximately 60 with respect to each other.

Though a ply-wood backing made of birch is- 60 preferred, the ply-wood backing may be made of `l any appropriate wood. I- have found that satis-A factory results arelsecured in the two-ply conv struction when one ply is formed, of poplar and the other of` gum wood. In the-:.three-ply em e5 bodiment, I have secured satisfactory results The thin 'resin coating also imparts increased v l utilizes three plies, though the plies may be so Y when the pliesare'formed of birch or maple, or

when two of the plies are formed of birch or maple, and the remaining ply formed of the other.

The thickness of the backing, of course, depends on the desired characteristics of exibility, stiffness, resiliency, etc. in the nal product.` In

' the two-ply embodiment, I have found that satisfactory results are obtained. when the total thickness of the ply-wood backing is from .020 to .050

Ainch. In the three-ply embodiment, I have resin, such as a heat-hardening phenolic resin.

Any abrasive grit may be used. Emery, lsilicon carbide, garnet, aluminum oxide, etc. are illustrative examples of abrasive gritswhich may be used. The size of the grains of the abrasive grit may vary from ne to coarse, depending on `the intended use of the product.

The abrasive grit is adhesively secured to the fibrous sheet material through the medium of any well-known adhesive, such as animal hide glue. l

The sheet material to which the abrasive grit and the ply-woodfbacking are adhesively secured may be formed of various materials. Though in the preferred form fibrous sheet material, such as p'aper, fabric and the like, is employed, it is to beA understood that other materials, such as parchment, vulcanized bers, impregnated materials and the like, may also be used.

'I'he adhesive for securing the ply-wood backing to the sheet material is one which sets to form a firm, flexible bond. The bond is sufliciently strong and rigid sothat it will flex and not break or separate during the intended use of the product. Animal glues or rubber adhesive compositions may be .mentioned as illustrative examples of adhesives which have given satisfactory results in adhesively securing the backing of the sheet material.

In the preferred form of the invention, an aqueous solution of a phenolic formaldehyde resin is utilized for completely coating the disks. Catabond #630 resin, manufactured and sold by the Catalin Corporation, is an illustrative example of a satisfactory phenolic formaldehyde resin which may be utilized. Since the resin is water-soluble, the viscosity thereof can be modiiied in accordance with the grain size of the grit. It is', of course, to be understood that the'nal resin coating isof a thickness which does not impair the desired function of the abrasive grit in the final product.

In order to more fully explain the nature of the invention, the embodiment thereof which relates to abrasive disks of the type and nature which are secured to portable grinding heads will now be described.

Referring now to the drawing, wherein an abrasive disk of the previously-mentioned type is illustratedand wherein like reference -numerals designate like parts, the reference numeral I designates generally the composite abrasive disk which comprises the ply-wood backing 2 to vwhich a sheet material (fabric) 3 is ad- -hesively secured by means of an adhesive 4 of the typeand nature previously described. n the free surface of the fabric, an abrasive grit 5 is adhesively secured by means of an adhesive i. also previously described.

The abrasive disk I is provided with a central aperture or opening 1, whereby said disk may be mounted `on a grinding head. To facilitate the mounting ofj the abrasive disk I on the grinding head, there is provided a pair of diametrically opposed slits l. vAs shown in the drawing. one end of each slit 8 communicates with the central opening 1, the opposite end of each slit 8 being provided1with a circular hole 9 whereby, when the disk `is,l mounted on the grinding head, the slits will not be* ripped beyond their desired termini. l

The abrasive disk* is provided with a coating II of a phenolic resin-which extends over all of the exposed surfacesoffthe disk. 'I'he coating I I not only extends over ythe top and bottom surfaces of the disk, butf'alsobver the entire circumferential wall of the diskand the peripheral walls of the holes I and 9, 'as-wellas the side walls of the slits 8.

Referring now to Figure 3,5iitwil1 be noted that in the form shown therein, the backing is composed of twoplies I0 and I2 adhesively secured together through the medium of the selected adhesive (not shown). It is to be noted that in this'embodixnent the plies I Ily and I2 are so arranged and disposed with respect to each other that-the grains I0' and I 2' of the plies I0 and I2 respectively are at approximately right angles to each other.

In Figure 4, there is illustrated a ply-wood backing formed of three plies I 5,-I6 and I1, the plies being adhesively secured together by means of a known adhesive (not shownl'.;v In this embodiment, it will be noted that thegrain I5' of the ply I5 is disposed at an angle, of approximately with respect to the grain` I6 of the ply I6 and that the `grain I'I' of ply I1 is disposed at an angle of approximately 607 with respect to the grain I6'. three-ply embodiment, the angularity between the grains in adjacent plies is approximately 60.

In producing the abrasive disk element, vone surface of the selected sheet material (fabric) 3, preferably of considerable length, is rendered tacky with the chosen adhesive, and the abrasive grit applied thereto. The grit-coated sheet material is dried for a time (about 1 to 2 minutes) to set the adhesive, and thereafter the chosen adhesive is applied to the grit surface and, after passing under a rubber roller whereby the quantity of adhesive is controlled and the grit surface sufficiently exposed to permit its desired function,', the material is dried. Thereafter, the selected adhesive is applied to the opposite surface of the sheet material or to the top surface of the ply-wood backing (which is coextensive to the sheet material 3) to which the sheet material is to be secured, or both of said surfaces,

and the materials preferably united under suflcient pressure to bring said material into intimate contact with each other. 'I'he resulting product is then-dried under controlled temperature and humidity conditions until all the excessive moisture is reduced to a minimum or eliminated from the product. The preferred conditions are approximately C. and a humidity of from 35%-50%. Under these conditions of temperature and humidity, I have found that satisfactory results are secured when the material is subjected thereto for at least 2 hours. Subsequently, the material is cut into disks on a power In other words, in the l 2,288,025 `press having a die which will stamp outthe formaldehyde resin. After. the disks have been coated as just described, they are subjected to heat (preferably in' an oven) for a period of about to 12 hours, at a temperature of l802i00 C.,

Vwhereby the phenolic resin is set to the waterproof, insoluble and infusible state. In the preferred form, heated air is circulated in the oven in order to insure` proper and uniform drying of all parts of the disk coated with the resin.

The ply-Wood backings are made by het pressing, as previously described, it being understood that-the various plies are arranged so that the grains thereof will runat the desired angles.

, Since it is obvious that variouschanges and modifications may be made in the above description without departing from the nature or spirit thereof, this invention is not restricted thereto except as set forth in the appended claims.

.-Iclaimz' one surface adhesively secured to said backing,'

and abrasive grit adhesively secured to the other Y one surface adhesively, secured to said backing,

surface of said sheet material, said disk element having a coating of a waterproof resin overval: the surfaces and edges thereof, said coating befing of a thickness which does not impair the desired function of the grit, -said disk element being suilicientlystiff so that it 'will lie flat and sufficiently resilient and flexible so that it willing a ply-wood backing, a vsheet material having and abrasive grit adhesively secured to the other surface of said sheet material, said' ply-Wood vbacking being formed of three plies so disposed4 with respect to each other that the grains of adjacent plies are at angles of approximately to each other. said disk element having a coating of a waterproof resin over al1 .the surfaces and edges thereof, said coating being of a thickness which'does not impair the desired function of the grit, said disk element being suiiiciently stiff so `that it will lie flat and suiliciently resilient and flexible so that it wil distortion without breaking.

5. A composite abrasive disk element comprising a ply-wood backing of a thickness not in excess of approximately .Q50 of an inch, a sheet material formed of fabric having one surface thereof adhesively secured to one surface of said backing, and abrasive grit adhesively secured to the other surface of said sheet material, said disk element having a coating of a waterproof phenolic resinover all the surfaces and edges thereof, said coating being of a thickness which does not impair the desired function of the grit, said disk element being suiiciently stiff so thatl it will lie flat and suiliciently resilientand flexible so that it will-permit appreciable distortion without breaking,

6. A composite abrasive disk element compris- Y ply-wood backing being formed of a plurality of one surface adhesively secured to said backing,

and abrasive grit adhesively secured to the other surface of said sheet material, said ply-wood backing being formed of a plurality of plies so disposed with respect to each otherthat the grain of each ply is at an angle to the other, said disk element having a coating of a waterproof resin over all the surfaces and edges thereof, said coating being of a thickness which does not im- -pair the desired function of the grit, said disk element being suiciently stiff so that it will lie flat and suiliciently resilient Aand exible so that material` formed of fabric having one surface it will permit appreciable distortion Awithout breaking.l l

, 3. A compositeabrasive disk element comprising a ply-wood backing, a sheet material having `1one surface adhesively secured to said backing,

and abrasive grit adhesively secured to the other surface of said sheet material, said ply-wood backing being formed of two plies so disposed with respect to each other that the grain of one "4"" ply isf at an angle of approximately 90 tether' of the other ply, said diskelement havgra f inghz` coating of a waterproof resin over all the surfaces and edges thereof, said coating beingV of a thickness which does not impair the desired function of the grit, said disk element bei sulliciently stili so that it will lie ilat. and iently resilient and flexible so that it will permit appreclable :distortion without breaking.

4. A composite abrasive disk element comprisin g a ply-wood backing, a sheet material having I plies so disposed with respect to each other that said disk element having acoating of a waterproof phenolic resin ever all the surfaces and edges thereof, said coating being of a thickness which does not impair the desired function of the grit, said disk element being suiiiciently stiff so that it will lie ilat and sufficiently resilient and exible so that it will permit appreciable distortion without breaking. Y

'1. A composite abrasive disk element comprising a ply-wood backing of athiclmess not in excess of approximately .050 of an inch, a sheet thereof adhesively secured to one surface of said backing, and abrasive grit'adhesively secured to the other surface of said sheet material, said ply-wood backing being formed of two pliesso disposed with respect to each other that the grain of one ply is at an angle-of approximately tothe grain of the other. ply, said disk element havinga coating of a waterproof phenolic resin over all the surfaces and edges thereof,

said coating being of a thickness which does not impair the desired function of the grit, said disk `element being sufficiently stiff so that it will lie flat and sulllclently resilient and exible s o that it will permit appreciable distortion without breaking.

8. A composite abrasive disk element comprising a ply-wood backing of a thickness' not in excessy of approximately .050 of an inch, a sheet material formed of fabric having one surface thereof adhesively secured to one surface of said backing.' and abrasive grit adhesively secured to the other surface of said sheet material, said disk element having a coating of a'waterproof phenolic resin over all the surfaces and edges thereof, said permit appreciable coating being of a thickness which does not impair the desired function of the grit, said plywood backing being formed of three plies so disposed with respect to each other that the grains of adiacent plies are at angles of approximately 60 to each other, said disk element being sufficiently stiff so that it will lie flat and sufficiently resilient and flexible so that it will permit appreciable distortion without breaking.

9. A composite abrasive disk element comprising a ply-wood backing, a sheet material having one surface adhesively secured to said backing, and abrasive grit adhesively secured by animal glue to the other surface of said sheet material, said disk element having substantially no free moisture and a coating of a waterproof resin over all the surfaces and edges thereof,

said coating being of a thickness which does not impair the desired function of the grit, said disk element being sufficiently stiff so that it will lie flat and sufficiently resilient and flexible so that it will permit appreciable distortion without 'plurality of plies so disposed with respect to each other that the grain of each ply is at an angle to the other, said disk element having substantially no free moisture and a coating of a waterproof resin over all the surfaces and edges thereof, said coating being of a thickness which does not impair the desired function of the grit, said disk element being sufficiently stiff so that it will lie fiat and sufiiciently resilient and flexible so that it will permit appreciable distortion without breaking.

11. A composite abrasive disk element comprising a ply-wood backing, a sheet material having one surface adhesively secured to said backing, and abrasive grit adhesively secured by animal glue .to-the other surface of said sheet material, said ply-wood backing being formed of'two plies so disposed with respect to each other that the grain of one ply is at an angle of approximately 90 to the grain of the other ply, said disk element having substantially no free moisture and a coating of a Waterproof resin over all the surfaces and edges thereof, said coating being of a thickness which does not impair the desiredv function of the grit, said disk element being sufciently stiff so that it will lie fiat and sufficiently resilient and flexible so that it will permit appreciable distortion without breaking.

12. A composite abrasive disk element comprising a ply-wood backing, a sheet material having one surface adhesively secured to said backing, and `abrasive grit adhesively secured by animal glue to the other surface of said sheet material, said ply-Wood backing being formed of three plies so disposed with respect to each other that the grains of adjacent plies are at angles of approximately to each other, said disk element having substantially no free moisture and a coating of a waterproof resin over all the surfaces and edges thereof, said coating being of a thick- .ness which does not impair the desired function of the grit, said disk element being sufficientlyV stiff so that it will lie flat and sufficiently resilient and flexible so that it will permit appreciable distortion without breaking.

l3. A composite abrasive. disk element comprising a ply-wood backing of a thickness ynot in excess of approximately .050 of an inch, a sheet material formed of-fabric having one sur face thereof adhesively secured to one surface of said backing, and abrasive grit adhesively secured by animal glue to the other surface of said sheet material, said disk element having substantially no free moisture and a coating of a water- `proof phenolic resin over all the surfaces and edges thereof, said coating being of a thickness which does notA impair the desired function of the grit, said disk element being sufficiently stiff so that it will lie fiat and sufliciently resilient and flexible so that it will permit appreciable distortion Without breaking.

14. A composite abrasive disk element comprising a ply-Wood backing of a thickness not in excess of approximately .050 of an inch, a sheet material formed of fabric having one surface thereof adhesively secured to one surface of said backing, and abrasive grit adhesively securedl by animal glue to the other surface of said sheet' material, said ply-wood backing being formed of a plurality of plies so disposed with respect to each other that the grain of each ply is at an angle to the other, said disk element having a substantially no free moisture and a coating of a waterproof phenolic resin over all the surfaces and edges thereof, said coating being of a thickness which does not impair the desired function of the grit, said disk element being sufficiently stiff so that it will lie flat and suiciently resilient and flexible so that it will permit appreciable distortion without breaking.

15. A composite abrasive disk element comprising a' ply-wood backing of a thickness not in.

excess of approximately .050 of an inch, a sheet material formed of fabric having one surface thereof adhesively secured by animal glue to one surface of said backing, and abrasive grit adhesively secured to the other surface of said sheet material, said ply-wood backing being formed of two plies so disposed with respect to each other that the grain of one ply is at an angle of approximately to the grain of the other ply, said disk element having substantially no free moisture and a coating of a waterproof phenolic resin over all the surfaces and edges thereof, said coating being of a thicknesszwhich does not impair the desired function' of the grit, said disk element being sufficiently stiff so that it will lie fiat and sufficiently resilient and flexible so that it will permit appreciable distortion Without breaking,

16. A composite abrasive disk element comprising a ply-wood backing of a thickness not in excess of approximately .050v of an inch, a sheet material formed of fabric having one surface thereof adhesively secured to one surface of said backing, and abrasive grit adhesively secured .by

animal glue to the other surface of said sheet material, said disk element having substantially no free moisture and a coating of a Waterproof phenolic resin over all the surfaces and edges thereof, said coating being of a thickness which does not impair the desired function of the grit, said ply-wood backing being formed of three plies so disposed with respect to each other that the grains of adjacent plies Vare at angles of approximately 60 to eachother, said disk element being suiliciently stiff so that it will lie fiat and sufficiently resilient and flexible so that it will permit appreciable distortion without breaking.

Nuno HLMSTEN.

Patent NQ. 2,288, 625

CRTIFICATE oF CORRECTION.

. July 7, 1911.2. NIILO HOLMSTEN.

It is hereby certified that error appears in the printed specification lof the above numbered patent requiring `coz'rectii on as follows: Page 2, first column, line )48, for "of the sheet" read --to the sheet--g and second column, line 22, for "`wel1a's read --fwell as; page 5*, first columnplines 2 and 5, strike out "on a power press having a die which will'stampoutthe disks"; page h., second column, line 26, claim llhafter "having" strike out "a; and that the said Letters Patent should be read with this corthe Patent office.

`rection therein that the -same may conform to the record of:I the case in signed and sealed this 18th day of August, A. D. 19142.

(Seal) Henry Van Arsdale, Acting Commissioner of' Patents. 

